Air-to-air atmospheric heat exchanger for condensing cooling tower effluent

ABSTRACT

A cooling tower having a heat exchanger. The heat exchanger includes at least one heat exchanger pack having a generally diamond shape. The heat exchanger pack includes a first set of passageways for receiving a stream of warm, water laden air and a second set of passageways for receiving ambient air. The first set of passageways and second set of passageways are separate. Cooling tower configurations including the heat exchanger pack are disclosed for achieving effluent plume abatement, and capture of a portion of the effluent for replacement back into the cooling tower reservoir or as a source of purified water.

PRIORITY

[0001] This application is a continuation-in-part, and claims thebenefit of, U.S. patent application Ser. Nos. 09/973,732 and 09/973,733,each filed Oct. 11, 2001, both entitled AIR-TO-AIR ATMOSPHERIC BEATEXCHANGER FOR CONDENSING COOLING TOWER EFFLUENT, the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to water reclamation fromcooling tower effluent or other heat rejection devices. Moreparticularly, the present invention relates to method and apparatus forreclaiming water from cooling tower effluent to provide a source ofclean water, reduce water consumption of the cooling tower, and/or toreduce the cooling tower plume.

BACKGROUND OF THE INVENTION

[0003] In electricity generation using steam driven turbines, water isheated by a burner to create steam which drives a turbine to createselectricity. In order to minimize the amount of clean water necessaryfor this process, the steam must be converted back into water, byremoving heat, so that the water can be reused in the process. In airconditioning systems for large buildings, air inside the building isforced passed coils containing a cooled refrigerant gas therebytransferring heat from inside the building into the refrigerant gas. Thewarmed refrigerant is then piped outside the building where the excessheat must be removed from the refrigerant so that the refrigerant gascan be re-cooled and the cooling process continued.

[0004] In both of the foregoing processes, and numerous other processesthat require the step of dissipating excess heat, cooling towers havebeen employed. In wet type cooling towers, water is pumped passed acondenser coil containing the heated steam, refrigerant, or other heatedliquid or gas, thereby transferring heat into the water. The water isthen pumped to the top of the cooling tower and sprayed over a coolingtower media comprised of thin sheets of material or splash bars. As thewater flows down the cooling tower media, ambient air is forced passedthe heated water and heat is transmitted from the water to the air byboth sensible and evaporative heat transfer. The air is then forced outof the cooling tower and dissipated into the surrounding air.

[0005] Cooling towers are highly efficient and cost effective means ofdissipating this excess heat and thus are widely used for this purpose.A recognized drawback to cooling towers, however, is that under certainatmospheric conditions a plume can be created by moisture from theheated water source evaporating into the air stream being carried out ofthe top of the cooling tower. Where the cooling tower is very large, asin the case of power plants, the plume can cause low lying fog in thevicinity of the cooling tower. The plume can also cause icing on roadsin the vicinity of the cooling tower where colder temperatures cause themoisture in the plume to freeze.

[0006] Efforts have therefore been made to limit or eliminate the plumecaused by cooling towers. Examples of such efforts can be found in thefollowing United States Patents:

[0007] U.S. Pat. No. 6,247,682 to Vouche describes a plume abatedcooling tower in which ambient air, in addition to being brought in atthe bottom of the tower and forced upwards through a fill pack as hotwater is sprayed down on the fill pack, is brought into the coolingtower through isolated heat conductive passageways below the hot waterspray heads. These passageways which are made from a heat conductivematerial such as aluminum, copper, etc., allow the ambient air to absorbsome of the heat without moisture being evaporated into the air. At thetop of the tower the wet laden heated air and the dry heated air aremixed thereby reducing the plume.

[0008] U.S. Pat. No. 4,361,524 to Howlett describes a plume preventionsystem in which the hot water is partially cooled before being providedinto the cooling tower. The partial cooling of the hot water isperformed using a separate heat exchanger operating with a separatecooling medium such as air or water. As discussed in the patent, theseparate heat exchanger reduces the efficiency of the cooling tower andthus should only be employed when atmospheric conditions exist in whicha plume would be created by the cooling tower.

[0009] Another example of a system designed to reduce plume in a wettype cooling tower can be found in the “Technical Paper Number TP93-01”of the Cooling Tower Institute 1993 Annual Meeting, “Plume Abatement andWater Conservation with the Wet/Dry Cooling Tower,” Paul A. Lindahl,Jr., et al. In the system described in this paper, hot water is firstpumped through a dry air cooling section where air is forced across heatexchange fins connected to the flow. The water, which has been partiallycooled, is then sprayed over a fill pack positioned below the dry aircooling section and air is forced through the fill pack to further coolthe water. The wet air is then forced upwards within the tower and mixedwith the heated dry air from the dry cooling process and forced out thetop of the tower.

[0010] While the foregoing systems provide useful solutions to the wetcooling tower plume problem, they all require the construction of acomplex and costly wet and dry air heat transfer mechanism. A simple andinexpensive wet and dry air cooling mechanism is still needed whereindry heated air and wet laden heated air can be mixed before passing outof the cooling tower to thereby reduce the plume.

[0011] Another recognized problem with cooling towers is that the waterused for cooling can become concentrated with contaminates. As waterevaporates out of the cooling tower, additional water is added but itshould be readily recognized that contaminants in the water will becomemore concentrated because they are not removed with the evaporate. Ifchemicals are added to the cooling water to treat the water thesechemicals can become highly concentrated which may be undesirable ifreleased into the environment. If seawater or waste water is used toreplace the evaporated water, a common practice where fresh water is notavailable or costly, salts and solids in the water can also build up inthe cooling water circuit As these contaminants become more concentratedthey can become caked in between the thin evaporating sheets diminishingthe towers cooling efficiency.

[0012] To prevent the foregoing problem it is a regular practice to“blowdown” a portion of the water with the concentrated contaminants andreplace it with fresh water from the source. While this prevents thecontaminants in the cooling tower water from becoming too concentrated,there may be environmental consequences to discharging water during theblowdown process. Efforts have therefore been made to reduce the waterconsumption in cooling towers.

[0013] U.S. Pat. No. 4,076,771 to Houx, et al. describes the currentstate-of-the-art in reducing the water consumption in a cooling tower.In the system described in this patent both cooling tower evaporativeheat transfer media and a coil section that transfers heat sensibly areprovided in the same system. The sensible heat transfer of the coilsprovides cooling of the process water but does not consume any water.

[0014] While the foregoing patent represents a significant advancementover prior art cooling towers, it would be desirable if a mechanism weredeveloped for recapturing water from the plume for replacement back intothe cooling tower water reservoir which did not require a coil sectionfor sensible heat transfer.

[0015] A separate problem that has been noted is the desalination of seawater, and purification of other water supplies, to create potabledrinking water. Numerous approaches have been developed to removepurified water from a moist air stream. The major commercial processesinclude Multi-Stage Flash Distillation, Multiple Effect Distillation,Vapor Compression Distillation, and Reverse Osmosis. See “The DesaltingABC's”, prepared by O. K. Buros for the International DesalinationAssociation, modified and reproduced by Research Department Saline WaterConversion Corporation, 1990. Examples of systems that use lowtemperature water for desalination or waste heat include the following:

[0016] “Zero Discharge Desalination”, Lu, et al., Proceedings from theADA North American Biennial Conference and Exposition, August 2000. Thispaper provides information on a device that produces fresh water from acold air stream and a warm moist air stream from a low grade waste heatsource. The fresh water is condensed along the walls separating the twoair streams. Also, a cold water is sprayed over the warm moist air toenhance condensation.

[0017] “Open Multiple Effect Desalination with Low Temperature ProcessHeat”, Baumgartner, et al., International Symposium on Desalination andWater Re-Use, Vol. 4, 1991. This paper provides information on a plastictube heat exchanger used for desalination that uses cold running wateron the inside of the plastic tubes and warm moist air flowing over theexterior of the tubes. The condensate forms on the outside of the coldtubes.

[0018] The foregoing show that there is a need for desalination systemsfor converting sea water, or other water supply containing high levelsof contaminants, into a purer water supply. A simple and cost effectivemeans of condensing the effluent of a cooling tower as a source of waterwould therefore be desirable.

SUMMARY OF THE INVENTION

[0019] In one aspect of the invention a heat exchanger is providedhaving a first set of passageways formed for receiving a first stream ofair. A second set of passageways for receiving a second stream of air isalso provided in the heat exchanger, the second stream of air beingwarmer than said first stream of air. Each passageway of the first setof passageways is separate but adjacent to at least one passageway ofthe second set of passageways so that heat from said second air streamwill be absorbed by the first air stream. A reservoir for capturingmoisture that condenses out of said second air stream is also provided.

[0020] In another aspect of the invention a heat exchanger is providedhaving two opposing walls configured with holes to allow for the passageof a first air stream. Tubes are provided between a hole in the firstwall and a corresponding hole in the second wall for channeling thefirst air stream there through. Walls provided between at least twoparallel edges of one wall and the corresponding parallel edges of saidsecond wall ensure that a second air stream can be channeled passed saidtubes to condensed moisture out of the second air stream.

[0021] In another aspect of the invention a method of reducing themoisture content of an air stream is provided wherein a first air streamhaving a flow rate between 10 and 80 pounds of dry air per square footper minute (pda/ft²/min) and a relative humidity at or above 90% isdirected through a first set of passageways. A second air stream havinga flow rate between 10 and 80 pda/ft²/min and a dry bulb temperature atleast five Fahrenheit degrees below the second stream is directedthrough a second set of passageways. Each passageway of the first set ofpassageways being separated from at least one passageway of the secondset of passageways by a thin heat conductive material. Heat from thesecond air stream is absorbed into the first air stream and watercondensed out of the second air stream is captured. In yet anotherembodiment of the invention, a cooling tower is provided having acounterflow evaporative media and a water distribution system thatdistributes hot water over the counterflow evaporative media. A heatexchanger that absorbs heat from a first air stream into a second airstream is also provided, the heat exchanger having a first set ofpassageways and a second set of passageways. A fan in the cooling towerdirects air through the counterflow evaporative media to create saidfirst air stream and directs the first air stream, having a flow ratebetween 10 and 80 pounds of dry air per square foot per minute(pda/ft²/min) and a relative humidity at or above 90%, through the firstset of passageways. The fan also directs the second air stream having aflow rate between 10 and 80 pda/ft²/min and a dry bulb temperature atleast five Fahrenheit degrees below the second stream through the secondset of passageways. Each passageway of the first set of passagewaysbeing separated from at least one passageway of the second set ofpassageways by a thin heat conductive material. A reservoir is providedfor capturing water condensed out of the first air stream.

[0022] In another aspect of the invention a cooling tower is providedhaving a fan at the top of the cooling tower for creating a negativepressure inside the cooling tower. A counterflow evaporative media isprovided along with spray heads that spray hot water onto thecounterflow evaporative media. A heat exchanger having a first set ofpassageways for passing an air stream from outside the cooling towerinto the center of the tower and a second set of passageways for passingan effluent air stream from the evaporative media is also provided inthe heat exchanger. The air stream from outside the cooling towerabsorbs heat from the effluent air stream and thereby condenses waterout of the effluent.

[0023] In yet another aspect of the invention, a cooling tower isprovided with a fan at the top of the cooling tower for creating anegative pressure inside the cooling tower. A crossflow evaporativemedia and a hot water distribution system that sprays hot water onto thecrossflow evaporative media are provided. A heat exchanger having afirst set of passageways for passing a first air stream from outside thecooling tower into the center of the tower and a second set ofpassageways for passing an effluent air stream from said evaporativemedia is provided. The air stream from outside the cooling tower absorbsheat from the effluent air stream and thereby condenses water out of theeffluent.

[0024] In another aspect of the present a cooling tower is provided andan inside and an outside and a longitudinal axis. The cooling towerincludes a evaporative media along with a liquid distribution systemthat distributes hot liquid over the evaporative media. The coolingtower also includes a heat exchanger that transfers heat from a firstair stream into a second air stream. The heat exchanger comprises atleast one generally diamond shaped heat exchanger pack having a firstset of passageways and a second set of passageways. The cooling towerfurther includes an air current generator that directs that directs thefirst air stream through the evaporative media and the first set ofpassageways. The air current generator also directs the second airstream through the second set of passageways.

[0025] In still another aspect of the present invention, an apparatusfor reducing the heat content of an air stream is provided. Theapparatus includes a means for directing a first air stream through afirst set of passageways of a generally diamond shaped heat exchanger.It also includes a means for directing a second air stream through aseparate, second set of passageways of the generally diamond shaped heatexchanger. The apparatus further includes a means for transferring heatform the first air stream into the second air stream.

[0026] In still yet another embodiment of thepresent invention, a methodfor reducing the heat content of an air stream is provided, comprisingthe steps of: directing a first air stream through a first set ofpassageways of a generally diamond shaped heat exchanger; directing asecond air stream through a separate, second set of passageways of thegenerally diamond shaped heat exchanger; and transferring heat from saidfirst air stream into said second air stream.

[0027] There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described below andwhich will form the subject matter of the claims appended hereto.

[0028] In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein, as well as the abstract, are for the purpose ofdescription and should not be regarded as limiting.

[0029] As such, those skilled in the art will appreciate that theconception upon which this disclosure is based may readily be utilizedas a basis for the designing of other structures, methods and systemsfor carrying out the several purposes of the present invention. It isimportant, therefore, that the claims be regarded as including suchequivalent constructions insofar as they do not depart from the spiritand scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a perspective view of a portion of a heat exchanger of apreferred embodiment of the invention.

[0031]FIG. 2 is a perspective view of a section of the heat exchanger ofFIG. 1 enlarged to show detail.

[0032]FIG. 3 is a graphical representation of a psychrometric chart fora heat exchanger.

[0033]FIG. 4 is a graphical representation of a psychrometric chart fora plume abatement process.

[0034]FIG. 5 is a graphical representation of a psychrometric chart fora plume abatement process with a moisture condensing heat exchanger.

[0035]FIG. 6 is a block diagram representation of a cooling tower inaccordance with a preferred embodiment of the invention.

[0036]FIGS. 7A and 7B are block diagram representations of a coolingtower in accordance with another preferred embodiment of the invention.

[0037]FIGS. 8A and 8B are block diagram representations of a coolingtower in accordance with another preferred embodiment of the invention.

[0038]FIG. 9 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0039]FIG. 10 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0040]FIG. 11 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0041]FIG. 12 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0042]FIG. 13 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0043]FIG. 14 is a block diagram representation of a cooling tower inaccordance with another preferred embodiment of the invention.

[0044]FIG. 15 is an illustration of a tubular heat exchanger inaccordance with a preferred embodiment of the present invention.

[0045]FIG. 16 is a block diagram representative of a cooling tower inaccordance with another preferred embodiment of the invention.

[0046]FIG. 17 is a block diagram representative of a cooling tower inaccordance with another preferred embodiment of the invention.

[0047]FIG. 18 is a longitudinal section view of a cooling tower inaccordance with an alternative embodiment of the, present invention.

[0048]FIG. 19 is a transverse section view of the cooling towerillustrated in FIG. 19.

[0049]FIG. 20 is a longitudinal section view of a cooling tower inaccordance with another alternative embodiment of the present invention.

[0050]FIG. 21 is a transverse section view of the cooling towerillustrated in FIG. 20.

[0051]FIG. 22 is a longitudinal section view of a cross-flow coolingtower in accordance with an alternative embodiment of the presentinvention.

[0052]FIG. 23 is a transverse section view of the cross-flow coolingtower illustrated in FIG. 22.

[0053]FIG. 24 is a side view of a plurality of heat exchanger packs thatmay be employed in a heat exchanger in accordance with an alternativeembodiment of the present invention.

[0054]FIG. 25 is a side view of a plurality of heat exchanger packs thatmay be employed in a heat exchanger in accordance with anotheralternative embodiment of the present invention.

[0055]FIG. 26 is a side view of a plurality of heat exchanger packs thatmay be employed in a heat exchanger in accordance with yet anotheralternative embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0056] Heat Exchanger Pack

[0057] Referring now to the figures wherein like reference numeralsindicate like elements, in FIG. 1 there is shown a vapor condensing heatexchanger pack 10. The heat exchanger pack 10 is constructed of thinsheets 12 that are bonded together to form a pack that has a first path14 and a second path 16 for two different air streams. In a preferredembodiment, the two air streams enter the heat exchanger pack 10 atright angles to each other and are kept separate by the thin sheets 12.

[0058] The thin sheets 12 are a relatively thin synthetic resin materialthat are shaped to assist in condensing vapor from a heated water ladenair stream passing through passageways 14 and transferring heat to acool air stream passing through passageways 16. In a preferredembodiment, the material is 0.005 to 0.040 inches in thickness but ispreferably 0.015 to 0.020 inches in thickness. The surface 18 may betextured to provide extended surface area presented to each of the airstreams with a minimal amount of resistance to the air stream flow.Examples of texture patterns appropriate for such use can be found inU.S. Pat. No. 5,944,094 to Kinney, Jr., et al. and U.S. Pat. No.3,995,689 to Cates, the disclosures of which are incorporated herein byreference. Other texture patterns may include but not be limited totextures such as dimples similar to golf ball texture and girded texturesimilar to a screen pattern embossed in the plastic sheet. Thisincreased surface area enhances the heat transfer capabilities of thethin sheet and increases the velocity fluctuations near the sheetsurface, which improves the local mixing of the individual air stream.The increased fluctuations and resulting local mixing of the air streamalso improves the heat transfer capabilities of the sheet.

[0059] As depicted in FIG. 2, to prevent the two air streams from mixingduring the heat exchange process, a seal 20 is formed in the thinsynthetic resin sheet on a first edge. This seal is formed by the raisededges 22 of the thin sheet material 12, on one edge of the sheets 12,that meet in the center of the air passageways 14, or in other words, israised one-half the width of the passageways 14. This edge seal 20extends along the length of the air passageway 14 parallel to the airpassageways 16.

[0060] Similarly, a seal 24 is formed by the raised edges 26 of the thinsheet material 12, on the edge perpendicular to the seal 20, that meetin the center of the air passageway 16, or in other words, is raised onehalf the width of the passageway 16. This edge seal 24 extends thelength of the air passageway 16 parallel to the air passageway 14.

[0061] Although not shown, the edge parallel to seal 20 and the edgeparallel to seal 24 are similarly bonded. Thus, perpendicularpassageways 14, 16 are formed within the heat exchanger pack.

[0062] One raised edge 26 extends positively off of the formed sheet andthe other 22 downward or negatively. In this arrangement a single sheetcomponent can be used to form the basis of the entire heat exchangerpack. This is accomplished when assembling the pack by stacking thesheets 12 on top of each other and turning over every other sheet andlocating it on the previous sheet. Although only three passageways aredepicted, it should be readily recognized that in use the heat exchangerpack will have many perpendicular passageways and that any number ofpassageways can be formed using the sheets 12 as disclosed herein.

[0063] To maintain the opening of the air pathways, spacer knobs orbuttons are formed in the thin sheet material. These buttons are spacedsimilarly to the edge seal and extend either positively 28 from theformed sheet or negatively 30 from the formed sheet a distance of halfof the width of the air passage opening. In a preferred embodiment, thebuttons 28 that extend positively are conidial in shape having a flattop surface when viewed in the direction of the air flow throughpassageway 16. When placed together the flat surfaces of the buttons ofone sheet are arranged opposite the flat surface of the buttons on theadjacent sheet. Each of the positively protruding buttons 28 extendsalong a length of the thin sheet parallel to the direction of airflow.In a preferred embodiment, the buttons 30 which protrude negatively havethe same shape as the buttons 28 that protrude positively but areperpendicular in orientation. Again, the negatively protruding buttons30 of one sheet are arranged opposite the negatively protruding buttonsof the adjacent sheet. An alternate spacer embodiment which positionsand interlocks the sheets may be found in Kinney '094.

[0064] The foregoing features are designed to maintain a consistentwidth of the air passageways and resist collapsing the passageways whena differential pressure is applied between the two passageways. Theconfiguration of the buttons is also designed to provide a minimalresistance to airflow while providing sufficient structural resistanceto collapse of the passageways.

[0065] The width of each of the passageways for either the cool airstream or the vapor laden air stream can be varied according to thedesign conditions of the particular task. Also, the cool air passageway16 and the vapor laden air passageway 14 do not necessarily have to beof equal widths. Practically, for the particular tasks of the currentinvention, the passageway widths would be at a minimum of 0.5 incheswide and a maximum of 3.0 inches wide with a preferred width between 1.0inches and 1.5 inches.

[0066] The overall dimensions of the completed pack of thin sheets arealso dependent on the particular design task associated with theinvention. However, the minimal pack size envisioned for the design is 2feet by 2 feet and the maximum is 6 feet by 24 feet.

[0067] The air entering the face of a heat exchanger pack ischaracterized by the mass flow over the gross face area. Typically thisis expressed as pounds of dry air per square foot of area per minute(pda/ft²/min). In the preferred embodiment, each set of air passages hasa mass flow rate between about 10 pda/ft²/min to about 60 pda/ft²/min.

[0068] The temperatures of the warm moist air stream for the preferredembodiment of the three processes, water conservation, waterpurification, and plume abatement, are typical of those experienced bycooling towers and other waste heat rejection devices. Thesetemperatures would range from a maximum of about 150 degrees F. to aminimum of about 40 degrees F. Evaporative cooling towers typicallydischarge air that is saturated or nearly saturated (about 100% relativehumidity). Similar evaporative devices that supply air with a relativehumidity of about 90% or higher are feasible for this invention. Airstreams with relative humidities below about 90% require significantsensible heat transfer to cool the air streams to their respective dewpoints. Condensation can only take place after the air stream reachesthe saturation curve at the dew point.

[0069] For the preferred embodiment the operating pressures for the heatexchanger pack will be about the same as typical cooling tower operatingpressures, in a range of +/−6 millibars. In general cooling towersoperate at or near atmospheric pressure. Cooling towers have axial fansand/or blowers, also known as centrifugal fans, that create slightchanges from atmospheric pressure to generate flow through the packingmedia, spray, and drift eliminators. These different components cause arestriction to the air flow by friction and velocity differentials hencea pressure change from atmospheric is required to force the air throughthe tower. These pressures are typically in a range of +/−3 millibarsfor axial fan systems and +/−6 millibars for systems with a blower. Itis customary to consider such cooling tower systems operating at theserelative small pressure differentials to be operating at atmosphericpressure.

[0070] General Condensation Process

[0071] As described, the vapor-condensing heat exchanger is arranged ina pack with passageways for two different air streams. In thepassageways 16 cool air is delivered from an outside source or from thesurrounding ambient air mass. The method of obtaining the cool air isdependent on the specific application for the device. The cool airtemperature will typically be significantly below the air masstemperature of the air stream in the opposing passageways 14. In theopposing passageway 14 warm moist air is delivered into the path. Thewarm moist air is typically saturated with water vapor or has a dry bulbtemperature that is at or near the resulting wet bulb temperature. Thisair mass is similar to that generated by a cooling tower which is usedto reject waste heat from a process. However, other processes andmethods that generate a similar warm moist air stream can be used forthe input into this device such as an evaporative condenser.

[0072] As shown in the psychrometric chart of FIG. 3, the warm moist airis at a point 32 on the depicted saturation curve. The location of thepoint 32 on the saturation curve where the warm moist air is indicatesthat it is 100% saturated with water vapor at a high temperature. Thecool air entering the other passageway is located at a point below thesaturation curve 34. The location of the cool air on the psychrometricchart indicates that it is at a lower temperature than the entering warmair. The moisture content associated with this air stream is generallynot relevant to the functionality of the device. In the case of plumeabatement, however, the moisture content of the entering air effects notonly the moisture content of the “mix”, but also the tangency of the mixline.

[0073] As the two air streams pass through the heat exchanger the warmair stream is cooled and the cold air stream increases in temperature.Because the two air streams do not physically contact each other, thecool air stream is heated in a way that no moisture is added or removedfrom the air stream. This is known as a sensible heating of the airstream. As noted on the psychrometric chart, upon exiting the heatexchanger the cool air has an increased temperature but the moisturecontent has been maintained constant 36.

[0074] The warm moist air is cooled from its initial point on thesaturation curve 32 to a lower temperature. As the warm moist air massis cooled the moisture content of the air stream must be reduced. Sincethe air stream is 100% saturated, water will condense out of the airstream and the resulting decrease in temperature will follow the 100%saturation curve to the new cooler temperature 38. The amount of heatlost in the warm saturated air stream must equal the amount of heatgained in the cool dry air stream.

[0075] Desalination research led to the serendipitous discovery that theexiting dry air of the air to air exchanger was much higher thanexpected. This discovery makes possible plume abatement with a devicepreviously assumed inadequate. Conventional wisdom suggested that anair-to-air heat exchanger for plume abatement is much less effectivethan a water-to-air heat exchanger such as coils or the plastic heatexchanger as disclosed by Kinney in '094. Cool ambient air is drawn fromoutside of the tower and heated sensibly. The heat source for warmingthis air would seem to favor water over air because of it's much largermass. For example the plastic heat exchanger in '094, typically has aflow rate of 20 gpm/sf or more. The mass flow rate then is typically 20gpm/sf×8.33 lbm/gallon=167 lbm/sf/min or more. The air-to-air heatexchanger as discussed above operates in a range from 10 to 80pda/sf/min. The total mass flow is determined by multiplying the dry airrate times (1+w_(s)) in which w_(s) is the humidity ratio. Assuming 100°F. saturated air, the humidity ratio, w_(s) is 0.0432. The mass of thisair stream varies from 10.4 to 83.5 lbm/sf/min. Therefore, the waterflow mass of the '094 plastic heat exchanger is typically several timesgreater than the air flow mass of the present invention. For comparableamounts of dry heat the air to air exchanger would seem to require achange in temperature of both air streams of several times that of thewater stream in the '094 heat exchanger. This was not thought to bepossible unless the surface was increased several times the surface areaof the water-to air heat exchanger to accomplish the same heat transfer.Therefore, the size of the air-to-air heat exchanger would seem toincrease to unmanageable or uneconomic proportions. However, using theheat exchanger of 10, FIG. 1., described previously the warm moist airstream is subject to a condensation process. In the condensationprocess, warm air comes in contact with a cool surface and watercondenses out of the air. In this process both sensible and latent heatare released and the absolute humidity is reduced. Since both latent andsensible heat is transferred in the device it becomes much moreefficient than previously thought possible.

[0076] In the passageway with the warm moist air 14, when the vaporcomes in contact with the cool surface of the cool passageway, dropletsof condensate are formed on the surface of the passageway with the warmmoist air stream. These droplets are a result of the warm moist airbeing cooled and the resulting moisture reduction of the air stream.These droplets coalesce on the sheet and flow down the warm moist airstream passageway surface of the sheet. The moisture that condenses ontothe sheet can either be collected at the base of the sheet or returnedinto the original source. The use of this water will be discussedfurther below.

[0077] Processes for Heat Exchanger

[0078] Water Conservation for Cooling Towers

[0079] As discussed in the previous section, warm moist air flowingthrough the heat exchanger passageway is cooled and the moisture contentis reduced. The reduction in moisture content of the warm air causesdroplets to be formed on the warm air passageway of the sheet. Thesedroplets coalesce and fall from the bottom of the sheet. The waterreclaimed from the moist air stream can be used to reduce the waterconsumption of a cooling tower apparatus.

[0080] Cooling towers reduce the temperature of process water through anevaporative process and thus provide a place to remove heat from asystem. The heat removed is typically not useful for other processes andlabeled “low grade waste heat” and is released to the surroundingatmosphere. Through the cooling tower process a certain percentage ofthe process water that is circulating through the system is lost due toevaporation. The amount of water lost through the evaporation process istypically between 0.5% to 3% of the total flow rate. Generally this isroughly 0.8% for every 10° F. of cooling of the process water. This lossof water can be costly to operators of cooling tower apparatuses.

[0081] The water leaving the tower through evaporation is in a purevapor state, therefore, other contaminants such as solids, dissolvedsolids, salts, etc., are left in the process water. Over time, as purewater is removed these contaminates build up in the process water. Toreduce the contaminants a certain percentage of the process water isremoved continually. The water removed from the system is calledblowdown. Therefore, to operate a cooling tower water must be added toboth compensate for the evaporation of the water and the requiredblowdown. In many instances this water is difficult to dischargedirectly into the environment because of the quality of the chemicalladen water and the increased regulations associated with dischargingwater. Therefore, there is a significant economic advantage in reducingthe amount of blowdown.

[0082] With the air to air heat exchanger 10, FIG. 1, described abovewater reclaimed from the warm moist air stream can be put back into thesystem. This will in effect reduce both the evaporation of the tower andthe required blowdown of the system. Configurations of a cooling towerincorporating this heat exchanger will be described below. Since thewater returned to the cooling tower system is nearly pure water, in manyinstances, it may be of better quality than the original make-up water.This improved water quality could also potentially reduce the amount ofchemicals required for the cooling tower process.

[0083] In order for the heat exchanger to operate effectively and returnwater back into the system, the air temperatures entering into the coolair passageway must be below the warm air entering the opposingpassageway. For a water conservation apparatus, as the two temperaturesbecome closer to the same value the amount of water returned to thebasin will be less. If the cool side of the heat exchanger is suppliedwith ambient air temperatures and not cooled by other means, the heatexchanger will return more water when the temperatures are cooler orduring winter operation. During summer operation the heat exchanger willreturn less water. Typical values of water returned back into the basinwill range from 40% of the evaporated water during the winter months to3% of the evaporated water during summer operation. Water returned on anannual basis would be around 10% to 30% depending on the location. Table1 below shows the percentage of evaporation water reclaimed for variouslocations in summer and winter. The numbers provided are for maximumwater reclaimed from cooling tower effluent based on local conditionsand a power plant duty of a 25-degree Fahrenheit range. Wyoming NevadaFlorida New York Saudi Arabia Summer 15%  3% 11% 16%  3% Winter 40% 23%21% 32% 14%

[0084] Water Purification and Desalination

[0085] A cooling tower generates warm moist air during theevaporation/heat rejection process. This warm moist air contains nearlypure vapor and is free of most contaminants such as solids, dissolvedsolids, salts, and chemicals. A significant portion of this pure vaporcan be recovered when this type of heat exchanger is employed. Inaddition to recycling the water back into the cooling tower reservoir,the pure vapor when converted back into the water state can be used forother applications that require a source of clean water. Because of theexpense associated with providing process water for cooling towers,often the make-up water used is either salt water from ocean sources orwastewater from an industrial process. When employed as a waterreclamation device this heat exchanger is capable of converting waterthat is otherwise undesirable because of the quality of water.

[0086] While not pure, the resultant water will be free of mostimpurities. Viruses, biological impurities, and a small amount ofdissolved solids may be entrained in the vapor. Also, a small amount ofprocess cooling water may also be entrained into the moist air streamand contaminate the condensed water. This type of carry over is termed“drift” in the cooling tower industry. A secondary purification processmay be employed to obtain further levels of desired water quality. Theadvantage provided by the present process can be seen in the case of seawater desalination to create potable water. In the case of desalinationof sea water, one of the most expensive steps in the process is removingthe salts. The foregoing cooling tower reclamation process could be usedto reduce the salt content considerably so that a less expensive processcould be used for the final purification of the water. An example of aprocess that can be used for the final purification process is reverseosmosis.

[0087] The process of recovering the water for other uses is essentiallythe same as has been described previously in the water conservationsection above with the exception that the water recovered from the heatexchanger pack can be collected in a separate basin. Details of acooling tower application with a recovery basin are described below.

[0088] As with the water conservation tower, if the surrounding air isused as the source for the cool side temperatures, as air temperaturesincrease during the summer months the production of clean water willdecrease. Typical water recovered from this system will be 20% to 25% ofthe total water evaporated on an annual basis. If a source of eithercold air or water is available more water could be reclaimed from thesystem. For example, if a source of cold ocean water is available itcould be used to cool the incoming air in the cold passageway of theheat exchanger. As the temperature difference increases between the warmand cold side of the heat exchanger sheet the condensation will increaseand thus more clean water will be generated. A configuration that wouldimprove the rate of clean water production when a source of coldseawater is available will be described below.

[0089] The water purification device is well suited for use in a coolingtower because of the generation of warm moist air, however other devicesthat generate warm moist air could also be used in conjunction with thisdevice.

[0090] Plume Abatement for Cooling Towers

[0091] The heat exchanger of the present invention can also be used toreduce the visible plume of a cooling tower. This process is essentiallythe same process as the water conservation process. The only differenceis the cold air heated in the cold side passageway is mixed with thewarm moisture laden air stream. The mixture of these two air streams caneffectively reduce the presence of the visible plume by an approachdifferent than typical plume abatement towers.

[0092] A typical method used to reduce the visible plume in a coolingtower is depicted on the psychrometric chart of FIG. 4. As depicted inthe chart, effluent air from the evaporative section of a cooling toweris warm 100% saturated air 40. Warm water from the heat source is alsosent through a coil or other heat exchanger located on the side of thetower. The warm water is used to heat the ambient air 42. Air is thenpulled through both the evaporative heat section and the water/air heatexchanger. The ambient air 42 that flows through the water/air heatexchanger is heated without any change in the moisture content (i.e.sensible heat transfer) 44. The warm dry air 44 then exits from theair/water heat exchanger.

[0093] The warm dry air stream 44 exiting the air/water heat exchangeris then mixed with the moist air stream 40 exiting the evaporativesection of the cooling tower. The mixture of these two air streamsresults in an air stream 46 which has the property that when the exitingcooling tower air stream 46 temperature and the ambient air temperature42 are connected with a line on a psychrometric chart, the connectingline 48 does not cross over the 100% saturation curve. If the connectingline 48 were to cross over the 100% saturation curve when the ambientand exiting air are mixed, condensation of the water vapor from the airstream of the evaporative section would occur creating a visible plumeor fog. The area above the 100% saturation curve is the super saturatedarea and is also termed the fog area. Therefore, systems are designedsuch that when the properties of the air mass exiting the cooling towersand the ambient air mass properties are mixed no visible plume willoccur for a given design condition.

[0094] Using the air to air heat exchanger 10, FIG. 1, of the presentinvention, the typical process is modified by reducing the moisturecontent of the air stream from the evaporative section and providing asource of warm dry heat to reduce the plume. The reduction in moistureof the warm moist air stream is a reduction in the absolute humidity ofthe air stream. The water content of the air from the evaporativesection of the cooling tower is reduced by use of the air to air heatexchanger as described above. The source of the warm dry air is theambient air that is heated in the heat exchanger from the cold airpassage.

[0095] The plume abatement process with the air to air heat exchanger ofthe present invention is depicted in the psychrometric chart of FIG. 5.As the exiting air from the cooling tower evaporative section 40 passesthrough the heat exchanger the temperature and moisture content arereduced 50. The ambient air, 42, is heated in the opposing passagewayresulting in a warmer dry air stream 52. The two air streams are mixedtogether forming a resultant air mass 54 below the saturation curve.When the ambient air mass 42 is mixed with the air mass from the mix ofthe two air streams 54 in the cooling tower the properties do not crossover into the super saturation area of the curve or the fog area. Thisis depicted by a line 56 connecting the ambient air mass 42 and themixed air mass 54 on the psychrometric chart.

[0096] The foregoing method for plume abatement is very effective forthe reduction of the plume because moisture that could cause a plume toform is partially removed from the tower before entering the surroundingambient conditions. The method is also less complicated because there isno water used in the heat exchanger system. Since no water is used inthe heat exchanger it eliminates the complexity of providing anotherpiping system for the cooling tower.

[0097] Cooling Tower Configurations

[0098] A first preferred embodiment of a cooling tower 58 employing theheat exchanger described above is depicted in FIG. 6. In thisconfiguration the heat exchanger 10 is located above the evaporativemedia 60 in a counterflow arrangement. This placement of the heatexchanger would be best suited for the water conservation and plumeabatement configurations. The process employed by this cooling tower isas described below.

[0099] Hot water from the heat source is pumped through a conduit havingspray heads 62 and sprayed over the evaporative media 60. An axial fan(or fans) 64 assist airflow of cool ambient air 66 through theevaporative media. In the evaporative media 60, the air is heated andmoisture is evaporated into the air stream. The heated waters laden airis then directed through air flow passageways 14 of the heat exchanger10. Ambient air 68 is also directed through separate passageways 16 ofthe heat exchanger perpendicular to the flow of the heated water ladenair. The cool ambient air 68 generates a cool surface on the heatexchanger 10 for the vapor to condense on. The condensate 15 will fallfrom the heat exchanger back into the main water collection area of thecooling tower. Condensate droplets size is exaggerated in the Figuresfor clarity. The two air streams 70, 72 exiting the heat exchanger 10are combined near the fan inlet.

[0100] The air-to-air heat exchanger 10 when incorporated into a coolingtower will create a resistance to the fan 64. The increased resistancewill require that the power be increased to the fan 64 in order tomaintain the same flow rate through the cooling section with theaddition of the heat exchanger 10. As depicted in FIGS. 7A and 7B,during operational times when more cooling tower performance isnecessary, air vent doors 74 located in the tower may be opened. Whenopening these doors 74 a significant amount of air will bypass the heatexchanger 10 and go directly to the fan 64. This will reduce the airresistance created by the heat exchanger 10 and increase the amount ofair that will flow through the cooling tower media 60. By increasing theairflow through the media 60, the performance of the cooling tower willincrease. However, when bypassing the heat exchanger 10 the waterconservation, water purification, and plume abatement processes arehalted.

[0101] An alternate embodiment of the doors are depicted in FIGS. 8A and8B. In this configuration the doors 76 not only provide a method toallow the warm moist air to bypass the heat exchanger 10, but alsoprovides a way to close off the cold side of the heat exchanger. Ineffect, becoming damper doors.

[0102] Another method to reduce the amount of resistance in the heatexchanger 10 is to increase the flow area of the heat exchanger pack. Asdepicted in FIG. 9, in order for two different air streams (warm moistair and cold ambient air) to flow through the single fan 64 of a coolingtower, a portion of the flow area from the cooling tower media isblocked off. Since a portion of the flow area is blocked off thevelocity of the air stream must be increased accordingly. This increasedvelocity of the flow creates more resistance when passing through theheat exchanger 10. In order to reduce the resistance, the heat exchangerflow area may be expanded by the amount of the blockage. In thisconfiguration the heat exchanger pack 10 is in effect cantileveredbeyond the cooling tower media 60. This reduces the velocity of the warmmoist air through the heat exchanger and reduces the amount of pressuredrop in the system.

[0103] A third way to configure the heat exchanger 10, as depicted inFIG. 10, is to tilt the heat exchanger pack 10 upward 80 toward the fan64. This configuration would provide an increased flow area for the heatexchanger and reduce the pressure drop as described previously. Thisconfiguration would also provide an improved air path for the airflowing on the inward-facing portion 68 of the heat exchanger 10 (coldpath), since the outlet of the pathway is positioned more towards thefan 64. The improved air path will result in less resistance andpressure drop for the heat exchanger cold side. Tilting heat exchanger10 may also be accomplished without cantilevering heat exchanger 10beyond cooling tower media 60.

[0104] In the configuration of FIG. 11 the length of the heat exchangerpack 10 has been reduced in the upper sections 82. In this configurationthe pressure drop of the system will be reduced because there is lessheat exchanger media for the warm moist air to travel through. It willalso provide better mixing of the moist air stream and the dry airstream. The mixing of the two air streams is important in the plumeabatement process in order to ensure that warm moist air does not mixwith the cold ambient air to form a fog. Similarly, as depicted in FIG.12, the lower portions of the heat exchanger pack 10 can be reduced 84to reduce pressure drop.

[0105] In an alternate embodiment of the cooling tower, the counterflowevaporative media is replaced with a crossflow media 86 as depicted inFIG. 13. The heat exchanger media 10 is located in the path of theexiting wet air stream in the plenum of the crossflow cooling tower. Theplacement of the heat exchanger 10 and evaporative media 86 in thisconfiguration would be best for the water purification and plumeabatement processes. The operation of this cooling tower is as describedbelow.

[0106] Hot water from the heat source is pumped to water distributionsystem 88 and distributed over the crossflow evaporative media 86. Anaxial fan 64 assists airflow of the ambient air 90 through theevaporative media 86 and through the inward-facing panel 16 of the heatexchanger 10. Air currents exiting the evaporative media 86 are directedupward through the outward-facing panel 14 of the vapor-condensing media(heat exchanger) 10. The cool ambient air 90 condenses the vapor on theoutward-facing panel. The condensate falls from the heat exchanger backinto reservoir 92 where it can be collected for other uses or returnedback into the main circulating water system. The air streams from boththe inward-facing panel and the outward-facing panel 94, 96 are combinednear the fan inlet.

[0107] It is to be further understood that the doors 74 and 76 as shownin FIGS. 7A, 7B, 8A, and 8B for counterflow cooling towers may bereadily incorporated in crossflow cooling tower configurations.Furthermore, the tilting of heat exchanger pack 10 and the stepping ofthe heat exchanger pack 10 as shown in FIGS. 10, 11, and 12 forcounterflow cooling towers may be readily incorporated in crossflowcooling towers.

[0108] During operation of the system as a water purification ordesalination system the ambient temperatures may not be cold enough toprovide the desired output of clean water from the condensation process.In order to boost the output of clean water from the heat exchanger 10 asecondary system may be required to reduce the temperature entering intothe cold side of the heat exchanger 10. As shown in FIG. 14, anotherbank of cooling tower heat transfer media 98 may be placed in front ofthe cold side entrance of the heat exchanger 10. The cooling tower media98 would be sprayed with cold water to chill the incoming air. Apossible source for the cold water may be an ocean source or other largebody of water that is cooler than the ambient dry bulb. If the wet bulbtemperature is low, the cold water source does not necessarily have tobe significantly colder than the ambient dry bulb. The air would thenenter in the cooling tower media and the temperature of the air reducedbefore entering into the cold side of the heat exchanger.

[0109] In an alternate embodiment depicted in FIG. 15, a tubular heatexchanger 100 is used to replace the thin resin synthetic sheet pack 10.This tubular heat exchanger will provide the same type of thermodynamicproperties as the thin resin synthetic sheet pack. The tubes 102 of thetubular heat exchanger could be made from a thin synthetic material asthe previously described heat exchanger or possibly a corrosionresistant metal such as galvanized stovepipe. These tubes 102 would beattached to a sheet 104 with holes so that the cold ambient air flowinginside the pipes 106 was separated from the warm moist air flowing overthe pipes 108. In a preferred embodiment, the tubes 102 are six inchesin diameter. The cooling tower configurations used with this type ofheat exchanger 100 are the same as shown previously.

[0110] In alternate embodiments of the cooling tower for counterflow,FIG. 16, and crossflow systems, FIG. 17, outside ambient air may beducted to heat exchanger packs 10 located in the plenum area through oneor more ducts 110. The packs would typically be in a staggered diagonalpattern. In this pattern the packs are not stacked directly above eachother, thereby reducing the total pressure drop in the system. Thisembodiment reduces the total amount of heat exchanger 10 required bysupplying cold ambient air to each heat exchanger section thus creatingmaximum heat transfer in each heat exchanger section. In thisconfiguration, the geometry provides better mixing by intermingling thetwo airstreams. This will assist in plume reduction.

[0111] Gas to gas heat exchangers that transfer heat between twodifferent gas streams are commonly used in industrial and powergeneration processes. One type of gas-to-gas heat exchanger is called aplate-fin heat exchanger. These heat exchangers are usually made ofmetal and consist of a flat sheet separated by a series of corrugatedsheets. The corrugated sheet serves to provide structural support to theheat exchanger and provide increased heat transfer by changing the flowstructure in the boundary layer and increased heat conductivity to theseparating plate (fin). The separating sheet, also known as the partingsheet, separates the two air streams and transfers the heat between thetwo gas streams by heat conductivity. See “Process Heat Transfer”,Hewitt, Shires, and Bott, CRC Press, Inc. 1994.

[0112] An advantage of the heat exchanger of the present invention isits lighter weight. For the preferred embodiment shown in FIG. 16, theoperating weight for a tower with 6′ bays is about 1100 lbs. Theoperating weight of an equivalently performing plastic heat exchanger,such as that of the Kinney '094 patent, is about 2200 lbs. Furthermore,the invention of '094 concentrates the weight at the outboard columns,whereas the weight of the heat exchanger in FIG. 16 is spread over 3bays. This reduces the amount of load added to individual columns. Lessweight or mass is also desirable for seismic design.

[0113] The present invention provides economic advantage overconventional plume abatement and water conservation. As previouslymentioned the air-to-air heat exchanger avoids the cost of having topipe hot water to the dry section of the cooling tower. Not only is thecost of the piping avoided, but also the additional cost of pumping thewater over the dry section is avoided. However, the fans experience anincrease in static pressure due to pulling the wet air stream throughthe air-to-air heat exchanger. The present invention requiresapproximately the same amount of power when compared to conventional 2pass coils with a siphon loop to minimize head or less power whencompared to single pass coils or the invention by Kinney in '094. In thelater case the total power saving can amount to about 15′ of head whichfor 200,000 gpm tower flow is about 900 horsepower. At $0.03/kw-hr thisis a savings of about $175,000 year.

[0114] Of more importance than the power savings are the maintenance andrequired water quality cost savings. Coils typically have 1″ to 1.25″diameter tubes. Larger tubes are typically not sufficient for therequired heat transfer. Water quality must be sufficient to preventfouling and plugging of the tubes. In the case of seawater or salt waterthe conventional finned tubes must be made of premium materials. Thismay be avoided by using the plastic heat exchanger as disclosed byKinney in '094, the disclosure of which is incorporated herein byreference. However, the heat exchanger water passages in Kinney '094 aremore restrictive than coils. If the water quality is not sufficient,filtration and or chemical treatment must be employed to improve andmaintain water quality. This can be expensive. The present inventionavoids the cost of improving and maintaining water quality. The moisturein the wet air stream is nearly pure which will not foul the air to airheat exchanger. Water quality less than has been thought possible forplume abatement or water conservation may be used with the presentinvention.

[0115] Also, some cooling tower applications may have water with debrislarger than the heat exchanger passageways which would plug thepassageways. An example is a “once through” power plant application inwhich water is extracted from a river or other body of water, heated bypassing through the condenser, and then sent to a cooling tower beforedischarging back into the body of water. The wet section of the coolingtower may have splash fill and large orifice water distribution nozzlessuch as disclosed in U.S. Pat. No. 4,700,893 issued to the presentassignee. The '893 invention has been commercialized with 1.875″ and2.5″ diameter orifices and could theoretically be larger. Therefore,water with debris larger than previously thought possible for plumeabatement can be used.

[0116] The wet section of the cooling tower may have splash fill andlarge orifice water distribution nozzles such as disclosed by Bugler inU.S. Pat. No. 4,700,893, the disclosure of which is incorporated hereinby reference. Thus fouling maintenance and water quality improvementcosts are avoided. This can have an economic impact of $1,000,000 peryear or more on a large power plant tower.

[0117] Finally, the initial capital cost of the present invention isless than that of the prior art. Plume abatement towers typically cost 2to 3 times the cost of a conventional wet only tower. For a large powerplant installation the plume abatement tower may cost $6,000,000 ormore. The savings of the present invention can be $1,000,000 or moreover conventional coil technology.

[0118] For desalination the cost per 1000 gallons of water is about$1.50 compared to $4 with multi-stage flash desalination and $3 forreverse osmosis. The present invention requires secondary treatment toproduce potable water. This adds about $0.50/1000 gallons. For a plantproducing 5 million gallons per day, this process can save $5,000 to$7,500 per day or about $2,000,000 annually.

[0119] The present invention provides plume abatement as a byproduct ontowers designed for desalination at no cost. Alternately, for coolingtower applications requiring plume abatement, desalination can be aby-product for the very little cost of collection by employing thisinvention.

[0120] Referring now to FIGS. 18 and 19, a cooling tower, generallydesignated 200, is illustrated in accordance with an alternativeembodiment of the present invention. The cooling tower 200 employs anair-to-air heat exchanger 202 similar to the heat exchanger described inthe previous embodiments, along with an air current generating devicesuch as a fan 204, which is disposed within a velocity recovery stack206. The fan 204 is powered by a motor 208. In the embodiment depictedin FIG. 18, the heat exchanger 202 includes a plurality of individualheat exchanger packs 210, similar to the exchanger packs 210 previouslydescribed embodiments. The individual exchanger packs 210 preferablyhave a generally diamond shape or diamond configuration. The coolingtower 200 also includes a series of ambient air ducts 212 each havingair inlets 214, along with a series of hot air passages 216 throughwhich hot, moist air, or effluent, travels. The ambient air ducts 212connect to the individual exchanger packs 210 as illustrated, so thatthe air ducts 212 are in communication with the path 16 through of theexchanger pack, as previously described in connection with FIG. 1. Thewarm air passages 216 are also connected to the individual exchangerpacks 210 as illustrated, however the warm air passages 216 are incommunication with the separate paths 14. Both the ambient air ducts 212and warm air passages 216 are positioned below the heat exchanger 202.As illustrated in FIG. 19, the ambient air ducts 212 preferably have aslanted or sloping base 217 that slants downwardly, away from thelongitudinal axis A of the cooling tower. This assists in helping theair flow in duct 212 to maintain a constant air stream velocity for moreuniform distribution to heat exchanger 202, however a slanted base 217is not required.

[0121] The cooling tower 200 also includes a hot liquid conduit 218having a series of hot water distributors or spraying nozzles 220 alongwith a drift eliminator 222 and a plurality of cooling tower, lower airinlets 224 located along the bottom portion of the cooling tower 200.The cooling tower 200 further includes evaporative heat transfer media226 disposed between the cooling tower lower air inlets 224 and thespraying nozzles.

[0122] In the cooling tower configuration depicted in FIG. 18, the heatexchanger packs 210 are preferably positioned adjacent to one another ina series so that the individual exchanger packs 210 abut one another,extending horizontally across the interior of the cooling tower. Theaforementioned positioning prevents the likelihood of the cooling towereffluent from bypassing the individual exchanger packs 210, andtherefore the heat exchanger 202, once it exits the evaporative heattransfer media 206. Alternatively, the heat exchanger 202 may include anadditional sealing or covering means (not pictured). The sealing meansmay be in the form of an applied material sealant such as a neopreneand/or silicon sealant, which can be applied to the abutting portions ofadjacent exchanger packs 210. The sealing means may alternativelyinclude an additional component or structure such as part of the coolingtower frame structure, disposed between adjacent heat exchanger packs210. The sealing means may be utilized in combination with theindividual exchanger packs 204 to compliment the abutting position ofthe exchanger packs 210, assisting in preventing the likelihood of thecooling tower effluent from bypassing the heat exchanger pack 210. Theindividual exchanger packs 210 of the heat exchanger 202 mayalternatively be positioned adjacent one another so that gap or spaceexists between the individual exchanger packs 210. In this embodiment,the sealing or covering means extends between the individual exchangerpacks 210 or to assist in preventing the likelihood of the effluent frombypassing the individual exchanger packs 210.

[0123] Referring now to FIG. 19, the sectional view of the cooling tower200 illustrated in FIG. 18 has been rotated 90 degrees to depict thetransverse section view of the cooling tower 200. As depicted in FIG.19, the present invention embodies cooling tower configurations that mayinclude dry air dampers or doors 228, which are disposed on the “drysection” of the cooling tower 200. The dry section of the cooling tower200 is generally designated 229 and is representative of the portion ofthe cooling tower 200 that is located above the drift eliminator 222.The cooling tower 200 may also include wet section dampers or doors 230which are disposed on the “wet section” of the cooling tower 200. Thewet section of the cooling tower 200 is generally designated 231 and isrepresentative of the portion of the cooling tower 200 that is locatedbelow the drift eliminator 222.

[0124] The dry air dampers 228 may be employed only, or in combinationwith the wet section dampers 230. Similarly, the wet section dampers 230may be singularly employed or employed in combination with the dry airdampers 228. The dry air dampers 228 and the wet section dampers 230function to regulate or throttle the flow of air through the coolingtower 200 during cooling tower operation.

[0125] During operation of the cooling tower 200, the fan 204 functionsto draw in ambient air into the cooling tower 200 simultaneously throughthe air inlets 214, 224. The ambient air that enters the cooling towerlower air inlets 224 is direct through the evaporative media 226 and maybe defined a first air stream, as indicated by the arrows 232. Theambient air that enters the air inlets 214 generates a second airstream, as indicated by arrows 234 that travels through the air ducts212. Hot liquid or water from the heat source is simultaneously pumpedthrough the hot liquid conduit 218, through the spray heads 220 andsprayed over the evaporative media 226.

[0126] While the first air stream 232 travels through the evaporativemedia 226, the air 232 is heated and moisture is evaporated into the airsteam 232. This heated, water laden air 232 or effluent, is thendirected through the drift eliminator 222. The effluent 232 thenproceeds to enter one of previous described the air flow passages of theheat exchanger packs 210. Meanwhile, as previously described, ambient,dry air 234 enters the air ducts 212 via the inlets 214 to generate thesecond air stream. The ambient, dry air 234 is then directed throughseparate air flow passages of the heat exchanger packs 210, preferablyperpendicular to the flow of the effluent 232. The ambient, dry air 234functions to generate a cool surface on the heat exchanger packs 210,allowing heat to transfer from the first air stream 232 to the secondair stream 234. The ambient, dry air 234 also provides a cool surface onthe heat exchanger packs 210 for water vapor from the effluent 232 orfirst air stream to condense on. As previously described in connectionthe embodiments depicted in FIGS. 1-17, the condensate from the effluent232 preferably fall from the exchanger packs 210 of the heat exchanger202 back into the main water collection area of the cooling tower (notpictured). As the two air streams 232, 234 exit the exchanger packs 210of the heat exchanger 202, they are combined near the fan inlet 236.

[0127] During operation, the dry air dampers 228 may be utilized alongwith the wet section dampers 230 to control the flow of the airstreams232, 234 through the cooling tower 200. Moreover, the dry air dampers228 may be closed completely, ceasing flow of ambient air through theair inlets 214 therefore closing off the “cold side” of the heatexchanger packs 210 of the heat exchanger 202.

[0128] Referring now to FIGS. 20 and 21, an alternative embodiment ofthe cooling tower 200 is illustrated, employing a two pass heatexchanger, generally designated 238. As depicted in FIGS. 20 and 21, thetwo pass heat exchanger 238 includes a first, lower series or tier 240of heat exchanger packs 210 and a second, complimentary upper series ortier 242 of heat exchanger packs 210 located above the first row 240.The heat exchanger packs 210 of the respective tiers 240, 242 arepreferably positioned adjacent to one another in a series abutting oneanother, so that they extend horizontally across the interior of thecooling tower 200. Furthermore, the vertical positioning of individualheat exchanger packs 210 of the lower tier 240 and the complimentaryupper tier 242 is preferably such that portions of the individual heatexchanger packs 210 also abut one another, similar to previouslydescribed horizontal positioning of the heat exchanger packs 210. Also,as is apparent from FIGS. 20 and 21, the individual heat exchanger packs210 of the respective tiers 240, 242, preferably mirror one another.However, the individual heat exchanger packs 210 positioned in therespective tiers 240, 242 may be offset from one another also.

[0129] As illustrated in FIGS. 20 and 21, the lower portions 243 of theheat exchanger packs 210 in the upper tier 242 are connected to, orcommunicate with, the upper portions 245 of the heat exchanger packslocated in the lower tier 240. This “communication” provides a single,continuous flow path for the warm, moist air or first air stream as ittravels through the first tier 240 of the heat exchanger 238 andtransitions to the second tier 242. Similarly, this “communication”provides a single, continuous path for the ambient air or second airstream 234, through the two tiers 240, 242 of the heat exchanger 238,that is separate from the flow path of the first air stream. The lowerportions 243 and the upper portions 245 of the heat exchanger packs 210are can be connected to one another via a sealing means as describedabove, or they may be connected via mechanical attachment such asbracket, bolt and/or screw. Alternatively, the tiers 240, 242 may be asingle, unitary piece.

[0130] Moreover, as described in previous embodiments, a sealing meansmay be utilized between heat exchanger packs 210 positioned horizontallyadjacent to one another within a tier 240, 242, and/or between heatexchanger packs positioned vertically adjacent to one another betweenthe tiers 240, 242. Alternatively, the upper and lower tiers, 240, 242may be spaced a distance apart and the sealing means may be utilized toextend between this gap to prevent the likelihood of effluent bypassingthe exchanger packs 210. In the aforementioned embodiment, the airstreams 232, 234 pass through two tiers 240, 242 of the heat exchangerpacks 210, increasing cooling and condensation of the first air stream.Furthermore, additional tiers (not illustrated) may be added to increaseheat exchange and to increase condensate of the first air stream.

[0131] Referring now to FIGS. 22 and 23, a cross-flow cooling tower,generally designated 300, is depicted in accordance with anotherembodiment of the present invention. Similar to the counter-flow coolingtowers illustrated in the previous embodiments, the cross-flow coolingtower 300 employs a heat exchanger 202 having generally diamond shapedexchanger packs 210. As is apparent from FIGS. 22 and 23 and the commonreference numerals, the cooling tower 300 includes like elementscompared to the previous embodiments. However, the cooling tower 300alternatively employs heat transfer fill media 302 in the cooling tower“wet section” where evaporative heat transfer occurs, such as film fillmedia. The cross-flow cooling tower 300 also employs a hot waterdistribution basin 304 which is located above the transfer fill media302.

[0132] Referring now to FIGS. 24-26, a plurality of heat exchanger packs304, is depicted in varying generally diamond shaped configurations,306, 308 and 310 respectively, in accordance with an alternativeembodiment of the present invention. As illustrated in FIGS. 24-26, theindividual heat exchanger packs 304 are non-square in shape or generallyrectangular, heat exchanger packs 304 arranged diagonally, point topoint, to form the generally diamond shaped configurations 306, 308,310. While the diamond shaped configurations 306, 308, 310 areillustrated in the two pass orientation as described in the previousembodiments, the diamond shaped configuration 306, 308, 310 mayalternatively be employed in the single pass orientation as previouslydescribed.

[0133] The many features and advantages of the invention are apparentfrom the detailed specification, and thus, it is intended by theappended claims to cover all such features and advantages of theinvention which fall within the true spirits and scope of the invention.Further, since numerous modifications and variations will readily occurto those skilled in the art, it is not desired to limit the invention tothe exact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

What is claimed is:
 1. A cooling tower having an outside and an insideand a longitudinal axis, comprising: an evaporative media; a liquiddistribution system that distributes hot liquid over said evaporativemedia; a heat exchanger that transfers heat from a first air stream intoa second air stream, said heat exchanger comprising at least onegenerally diamond shaped heat exchanger pack that includes a first setof passageways and a second set of passageways; and an air currentgenerator that directs said first air stream through said evaporativemedia and through said first set passageway and wherein said air currentgenerator directs said second air stream through said second set ofpassageways.
 2. The cooling tower according to claim 1, wherein said atleast one generally diamond shaped heat exchanger pack is a plurality ofgenerally diamond shaped heat exchanger packs, each of said plurality ofgenerally diamond shaped heat exchanger packs having said first set ofpassageways and said second set of passageways, wherein said pluralityof generally diamond shaped heat exchanger packs are positioned adjacentto each other so that a portion of each of said plurality of generallydiamond shaped heat exchanger packs abut one another so that said heatexchanger extends across the inside of the cooling tower to form asingle tier heat exchanger.
 3. The cooling tower according to claim 2,further comprising: a first plurality of air ducts that open to theinside of the cooling tower, wherein said first plurality of air ductsconnect to said first set of passageways of said plurality of generallydiamond shaped heat exchanger packs; and a second plurality of air ductsthat open to the outside of the cooling tower, wherein said secondplurality of air ducts connect to said second set of passageways of saidplurality of generally diamond shaped heat exchanger packs.
 4. Thecooling tower according to claim 3, wherein said first plurality of airducts each comprise side portions, and wherein said second plurality ofair ducts each comprise side portions and base portions, wherein saidbase portions are angled generally downwardly away from the longitudinalaxis of the cooling tower.
 5. The cooling tower according to claim 1,further comprising a reservoir that captures water condensed out of saidfirst air stream.
 6. The cooling tower according to claim 1, whereinsaid evaporative media is counterflow evaporative media.
 7. The coolingtower according to claim 1, wherein said evaporative media is crossflowevaporative media.
 8. The cooling tower according to claim 1, furthercomprising a drift eliminator disposed above said evaporative media. 9.The cooling tower according to claim 1, further comprising a set ofdoors that control air flow through said first set of air passageways.10. The cooling tower according to claim 1, further comprising a set ofdoors that control air flow through said second set of air passageways.11. The cooling tower according to claim 1, further comprising: a firstset of doors that control air flow through said first set of airpassageways; and a second set of doors that control air flow throughsaid second set of air passageways.
 12. The cooling tower according toclaim 1, wherein said liquid distribution system comprises a pluralityof nozzles that distribute hot water over said evaporative media. 13.The cooling tower according to claim 1, wherein said first passagewayand said second passageway are formed by sandwiching thin sheetstogether.
 14. The cooling tower of claim 13, further comprisingpositively raised edges along two parallel edges of the thin sheetmaterial and negatively raised edges along the two parallel edges of thethin sheets perpendicular to the edges having the positively raisededges; said first passageway being formed by reversing two sheets andbonding the positively raised edges on one side together and thepositively raised edges on the other side together; and said secondpassageways being formed by reversing two sheets and bonding thenegatively raised edges on one side together and the negatively raisededges on the other side together.
 15. The cooling tower of claim 14,wherein said first passageways are oriented perpendicular to said secondpassageways by alternately bonding the negatively raised edges and thepositively raised edges in a set of thin sheets.
 16. The cooling towerof claim 15, further comprising positively and negatively formed buttonsin the thin sheets for maintaining the passageways open underdifferential pressure between said first passageways and said secondpassageways.
 17. The cooling tower according to claim 16, wherein thepositively formed buttons on a first sheet press against the positivelyformed buttons on a first adjacent sheet and the negatively formedbuttons press against the negatively formed buttons on a second adjacentsheet.
 18. The cooling tower according to claim 17, wherein thepositively formed buttons are configured to reduce resistance to flow ofthe first air stream in a first direction and the negatively formedbuttons are configured to reduce resistance to flow of the second airstream in a second direction.
 19. The cooling tower according to claim13, wherein said thin sheets are made of a synthetic resin film.
 20. Thecooling tower according to claim 13, wherein said thin sheets are madeof polyvinyl chloride (PVC).
 21. The cooling tower according to claim 1,wherein said plurality of diamond shaped heat exchanger packs arepositioned adjacent to one another along the longitudinal axis to form atwo-tier heat exchanger.
 22. The cooling tower according to claim 2,further comprising a sealing means that seals the abutting portions ofthe plurality of heat exchanger packs.
 23. The cooling tower accordingto claim 1, wherein said air current generator is a fan.
 24. A methodfor reducing the heat content of an air stream, comprising: directing afirst air stream through a first set of passageways of a generallydiamond shaped heat exchanger; directing a second air stream through aseparate, second set of passageways of the generally diamond shaped heatexchanger; and transferring heat from said first air stream into saidsecond air stream.
 25. The method according to claim 24, furthercomprising: condensing water out of the first air stream; and capturingthe water condensed out the first air stream in a reservoir.
 26. Anapparatus for reducing the heat content of an air stream, comprising:means for directing a first air stream through a first set ofpassageways of a generally diamond shaped heat exchanger; means fordirecting a second air stream through a separate, second set ofpassageways of the generally diamond shaped heat exchanger; and meansfor transferring heat from said first air stream into said second airstream.